In a reciprocating piston engine, a connecting rod connects a piston to a crank or crankshaft. Rotational movement of the crankshaft rotates the connecting rod about the central axis of the crankshaft, which causes linear movement of the piston.
Connecting rods can be made of steel, aluminum, or the like. Modern, typical connecting rods are either forged or sintered, but other methods of manufacturing are known. Connecting rods can initially be formed as one solid piece (through the forging, sintering, etc.). After a connecting rod has been formed and allowed to cool, it can be severed to create a line of separation near the main opening of the rod. The rod is thus broken into two pieces. This allows the rod to be assembled over the crankshaft, at which time the rod is bolted or otherwise fastened back together around the crankshaft.